RFID systems may include RFID tags and RFID readers (the latter may also be known as RFID reader/writers or RFID interrogators). RFID systems can be used in many ways, including locating and identifying objects to which the tags are attached. RFID systems are particularly useful in product-related and service-related industries for tracking large numbers of objects being processed, inventoried, or handled. In such cases, an RFID tag is usually attached to an individual item, or to its package.
In principle, RFID techniques entail using an RFID reader to interrogate one or more RFID tags. The reader transmitting a Radio Frequency (RF) wave performs the interrogation. A tag that senses the interrogating RF wave responds by transmitting back another RF wave. The tag generates the transmitted back RF wave either originally, or by reflecting back a portion of the interrogating RF wave in a process known as backscatter. Backscatter may take place in a number of ways.
The reflected-back RF wave may further encode data stored internally in the tag, such as a number. The response may be demodulated and decoded by the reader, which thereby identifies, counts, or otherwise interacts with the associated item. The decoded data can denote a serial number, a price, a date, a destination, other attribute(s), any combination of attributes, and so on.
An RFID tag typically includes an antenna system, a power management section, a radio section, and frequently a logic section, a memory, or both. In earlier RFID tags, the power management section included an energy storage device, such as a battery. RFID tags with such an energy storage device are known as active tags. Advances in semiconductor technology have miniaturized the electronics so much that many RFID tags can be powered solely by the received RF signal. Such RFID tags do not include an energy storage device, and are called passive tags.
As technology continues to advance, customers have focused on the desire to reduce power usage, as well as producing an increased number of devices using the same wafer size. Thus, there is a need for RFID circuitry, including circuitry used in RFID tags, that uses less power, and less die real estate.